Boats, recreation or snow vehicles:  the purchaser must file Form ST-6 by using the Online ST-6 Application and pay the use tax by the twentieth day of the month following the purchase, use, storage, or other consumption of such boat, recreation or snow vehicle within Massachusetts.  ST-6 Application Information  

Boats, Recreational & Snow Vehicle Resources  
Boat Excise Information 
Boat, Recreational Vehicle and Snowmobile Registration
Motor Vehicle Sales and Use Tax Information
Motor Vehicle Excise Information
Guide to Sales and Use Tax